For convenience, the grounding connection of this invention should be made through an inexpensive, factory-applied device which becomes part of the cable reel thereby eliminating the high labor cost and time for applying such devices in the field. Such devices must permit the reel to be rotated, while the cable is being pulled off during installation, on either a shaft and jack stand or a shaftless floor roller pay-off apparatus.
The invention consists of an assembly of two separate parts which may be stamped or otherwise formed, and preferably made as interlocking metal plates with ball bearings in a race between the plates. The race is located concentrically with respect to a center hole of the cable reel, the two plates being free to rotate independently of each other in a plane perpendicular to the center hole of the reel. One plate is fastened to the side of the reel with the center hole of the plate aligned concentrically around the reel arbor hole, and this plate is electrically connected to the inside end of the metal clad cable on the reel. The outer plate is connected to a grounding cable, and this outer plate preferably makes electrical connection to the inner plate through ball bearings located between the plates, and which are used to permit relative movement of the plates with minimum friction, and through the interlocked edges of the plates and leaf springs between them in the preferred embodiment of the invention.
The reel and inner plate are free to rotate while the stationary outer plate is connected to the ground. This ground connection device permits the reel to be mounted on a shaft through its center arbor hole where a shaft and jack stand pay-off arrangement is used, or the reel may be mounted on floor rollers where this type of pay-off is desired.
This invention is quickly and easily installed at the cable factory to reels of cable by means of sheet metal screws. One screw is run through the inner plate and the cable end to make the electrical and mechanical connection between the plate and cable, and additional screws are used to fasten the inner plate to the reel flange.
Ground wire connection to the outer plate may be made as shown in the drawings. For greater convenience, a quick connect means is desirable to save time in the field, and this is accomplished by factory welding a steel tube to the outer plate, and in the field, simply inserting a snug fitting metal rod which is attached to the grounding wire. This allows the grounding wire to be quickly attached and removed when the reel must be moved to different locations for installation of the cable. The rod may be held in the tube by a set screw or by resilient indents formed in the wall of the tube.
Other options, features and advantages of the invention will appear or be pointed out as the description proceeds.